Microalgae Characterization for Consolidated and New Application in Human Food, Animal Feed and Nutraceuticals

Sustainable microalgal biomass as a potential functional food and its applications in food industry: a comprehensive review

Microalgae (MA) are the most abundant seaweeds with high nutritional properties. They are accepted as potential biocatalysts for the bioremediation of wastewater. They are widely used in food, feed, and biofuel industries and can potentially be food for future generations. MA-based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. They provide a wide range of functional components, viz. omega-3 fatty acids, along with a plenteous number of pigments such as ß-carotene, astaxanthin, lutein, phycocyanin, and chlorophyll, which are used extensively as food additives and nutraceuticals. Further, proteins, lipids, vitamins, and carbohydrates are described as nutritional characteristics in MA. They are investigated as single-cell protein, thickening/stabilizing agents, and pigment sources in the food industry. The review emphasizes the production and extraction of nutritional and functional components of algal biomass and the role of microalgal polysaccharides in digestion and nutritional absorption in the gastrointestinal tract. Further, the use of MA in the food industry was also investigated along with their potential therapeutic applications.

Dietary supplementation with Dunaliella salina microalga promotes quail growth by altering lipid profile and immunity

The goals of the current research are to ascertain the impacts of Dunaliella salina (DS) on quail growth, carcass criteria, liver and kidney functions, lipid profile, and immune response. Two hundred and forty 7-day-old quail chicks were divided equally into 4 separate groups with 6 replicates with 10 birds each. The groups were as follows: 1) control diet (the basal feed without DS), 2) control diet enriched with 0.25 g DS/kg, 3) control diet enriched with 0.50 g DS/kg, and 4) control diet enriched with 1.00 g DS/kg. Results elucidated that the birds which consumed 0.5 and 1 g DS/kg diet performed better than other birds in terms of live body weight (LBW), body weight gain (BWG), and feed conversion ratio (FCR). There were no significant changes in feed intake (FI) and carcass characteristics due to different dietary DS levels. Compared to the control group, DS-treated groups had better lipid profile (low total cholesterol and LDL values and high HDL values) and immune response (complement 3 values). The quails consumed feeds with different levels of DS had greater (P < 0.038) C3 compared to control. Adding 0.5 and 1 g DS/kg lowered blood concentrations of triglycerides and total protein (TP) values. The high level of DS (1 g/kg) had higher albumin values and lower AST values than other groups (P < 0.05). The creatinine values were at the lowest levels in the group consumed 0.50 g DS/kg feed. No changes (P > 0.05) were demonstrated among experimental groups in the ALT, urea, and lysozyme values. In conclusion, adding D. salina to growing quail diets enhanced growth, immune system, blood lipid profile, and kidney and liver function.

Dietary supplementation with a mixture of Dunaliella salina and Spirulina enhances broiler performance by improving growth, immunity, digestive enzymes and gut microbiota

The aim of this study is to evaluate the effect of Dunaliella salina and Spirulina (D + S) mixture on performance, carcass yield, kidney and liver markers, lipid profile, and immune responses of fattening chicks. Two hundred broiler chicks at 7 days old were distributed into 5 experimental groups, 5 replicates each with 8 chicks each. Group 1 was fed on only basal diet; group 2 was fed with basal diet and 0.50 g/kg (D + S); group 3 was fed with basal diet and 1.00 g/kg (D + S); group 4 was fed with basal diet and 1.50 g/kg (D + S); and group 5 was fed with basal diet supplemented with 2.00 g/kg (D + S). The additive mixture (D + S) consisted of (1 D. salina: 1 Spirulina). The experiment lasted for 6 wk. The results demonstrated significantly improved better live body weight, body weight gain, and feed conversion ratio (P<0.01) for groups that received (D + S) at levels of 1.0 and 1.5 g/kg diet compared to other groups at 6 wk of age. There was no significant influence of different levels of dietary feed additives on feed intake or carcass traits. The lipid profile was improved through a reduction of total cholesterol and low-density lipoprotein (LDL) values and increasing high-density lipoprotein (HDL) values, as well as the immune response, which was improved through increasing values of complement 3, immunoglobulin M (IgM), and immunoglobulin G (IgG) in the birds treated with (D + S) compared to the control group. The inclusion of all levels of (D + S)/kg decreased triglyceride, while total protein, albumen, and globulin values (P<0.05 or P<0.01) were higher compared to other groups. The inclusion of the different levels of (D + S)/kg improved liver function, whereas aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values were lower than in other groups (P<0.001). The lowest values of creatinine, urea, and uric acid were noted in birds fed a diet supplemented with 1.50 g (D + S)/kg. Antioxidant levels were improved through increasing values of catalase (CAT) and reduced glutathione (GSH) enzymes in the treated birds with (D + S) compared with the control chicks. Furthermore, digestive enzymes and microbial content were improved in broiler checks fed on diet supplemented with (D + S) compared to the control group. In conclusion, supplementing broiler chicks with a dietary D. salina and Spirulina combination increased their productive performance, immunity, kidney and liver function, lipid profile, and digestive enzymes.

The Clinical Promise of Microalgae in Rheumatoid Arthritis: From Natural Compounds to Recombinant Therapeutics

Rheumatoid arthritis (RA) is an invalidating chronic autoimmune disorder characterized by joint inflammation and progressive bone damage. Dietary intervention is an important component in the treatment of RA to mitigate oxidative stress, a major pathogenic driver of the disease. Alongside traditional sources of antioxidants, microalgae-a diverse group of photosynthetic prokaryotes and eukaryotes-are emerging as anti-inflammatory and immunomodulatory food supplements. Several species accumulate therapeutic metabolites-mainly lipids and pigments-which interfere in the pro-inflammatory pathways involved in RA and other chronic inflammatory conditions. The advancement of the clinical uses of microalgae requires the continuous exploration of phytoplankton biodiversity and chemodiversity, followed by the domestication of wild strains into reliable producers of said metabolites. In addition, the tractability of microalgal genomes offers unprecedented possibilities to establish photosynthetic microbes as light-driven biofactories of heterologous immunotherapeutics. Here, we review the evidence-based anti-inflammatory mechanisms of microalgal metabolites and provide a detailed coverage of the genetic engineering strategies to enhance the yields of endogenous compounds and to develop innovative bioproducts.

Biomanufacturing of glycosylated antibodies: Challenges, solutions, and future prospects

Traditionally, recombinant protein production has been done in several expression hosts of bacteria, fungi, and majorly CHO (Chinese Hamster Ovary) cells; few have high production costs and are susceptible to harmful toxin contamination. Green algae have the potential to produce recombinant proteins in a more sustainable manner. Microalgal diversity leads to offer excellent opportunities to produce glycosylated antibodies. An antibody with humanized glycans plays a crucial role in cellular communication that works to regulate cells and molecules, to control disease, and to stimulate immunity. Therefore, it becomes necessary to understand the role of abiotic factors (light, temperature, pH, etc.) in the production of bioactive molecules and molecular mechanisms of product synthesis from microalgae which would lead to harnessing the potential of algal bio-refinery. However, the potential of microalgae as the source of bio-refinery has been less explored. In the present review, omics approaches for microalgal engineering, methods of humanized glycoproteins production focusing majorly on N-glycosylation pathways, light-based regulation of glycosylation machinery, and production of antibodies with humanized glycans in microalgae with a major emphasis on modulation of post-translation machinery of microalgae which might play a role in better understanding of microalgal potential as a source for antibody production along with future perspectives.

Microalgae as a Sustainable Source of Antioxidants in Animal Nutrition, Health and Livestock Development

Microalgae are a renewable and sustainable source of bioactive compounds, such as essential amino acids, polyunsaturated fatty acids, and antioxidant compounds, that have been documented to have beneficial effects on nutrition and health. Among these natural products, the demand for natural antioxidants, as an alternative to synthetic antioxidants, has increased. The antioxidant activity of microalgae significantly varies between species and depends on growth conditions. In the last decade, microalgae have been explored in livestock animals as feed additives with the aim of improving both animals' health and performance as well as product quality and the environmental impact of livestock. These findings are highly dependent on the composition of microalgae strain and their amount in the diet. The use of carbohydrate-active enzymes can increase nutrient bioavailability as a consequence of recalcitrant microalgae cell wall degradation, making it a promising strategy for monogastric nutrition for improving livestock productivity. The use of microalgae as an alternative to conventional feedstuffs is becoming increasingly important due to food-feed competition, land degradation, water deprivation, and climate change. However, the cost-effective production and use of microalgae is a major challenge in the near future, and their cultivation technology should be improved by reducing production costs, thus increasing profitability.

More Than Pigments: The Potential of Astaxanthin and Bacterioruberin-Based Nanomedicines

Carotenoids are natural products regulated by the food sector, currently used as feed dyes and as antioxidants in dietary supplements and composing functional foods for human consumption. Of the nearly one thousand carotenoids described to date, only retinoids, derived from beta carotene, have the status of a drug and are regulated by the pharmaceutical sector. In this review, we address a novel field: the transformation of xanthophylls, particularly the highly marketed astaxanthin and the practically unknown bacterioruberin, in therapeutic agents by altering their pharmacokinetics, biodistribution, and pharmacodynamics through their formulation as nanomedicines. The antioxidant activity of xanthophylls is mediated by routes different from those of the classical oral anti-inflammatory drugs such as corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs): remarkably, xanthophylls lack therapeutic activity but also lack toxicity. Formulated as nanomedicines, xanthophylls gain therapeutic activity by mechanisms other than increased bioavailability. Loaded into ad hoc tailored nanoparticles to protect their structure throughout storage and during gastrointestinal transit or skin penetration, xanthophylls can be targeted and delivered to selected inflamed cell groups, achieving a massive intracellular concentration after endocytosis of small doses of formulation. Most first reports showing the activities of oral and topical anti-inflammatory xanthophyll-based nanomedicines against chronic diseases such as inflammatory bowel disease, psoriasis, atopic dermatitis, and dry eye disease emerged between 2020 and 2023. Here we discuss in detail their preclinical performance, mostly targeted vesicular and polymeric nanoparticles, on cellular models and in vivo. The results, although preliminary, are auspicious enough to speculate upon their potential use for oral or topical administration in the treatment of chronic inflammatory diseases.

Variability in Macro- and Micronutrients of 15 Rarely Researched Microalgae

Microalgae have enormous potential for human nutrition, yet the European Commission has authorized the consumption of only eleven species. Strains of fifteen rarely researched microalgae from two kingdoms were screened regarding their nutritional profile and value for human health in two cultivation phases. Contents of protein, fiber, lipids, fatty acids, minerals, trace elements and heavy metals were determined. In the growth phase, microalgae accumulated more arginine, histidine, ornithine, pure and crude protein, Mg, Mn, Fe and Zn and less Ni, Mo and I₂ compared to the stationary phase. Higher contents of total fat, C14:0, C14:1_n5, C16:1_n7, C20:4_n6, C20:5_n3 and also As were observed in microalgae from the chromista kingdom in comparison to microalgae from the plantae kingdom (p < 0.05). Conversely, the latter had higher contents of C20:0, C20:1_n9 and C18:3_n3 as well as Ca and Pb (p < 0.05). More precisely, Chrysotila carterae appeared to have great potential for human nutrition because of its high nutrient contents such as fibers, carotenoids, C20:6_n3, Mg, Ca, Mn, Fe, Se, Zn, Ni, Mo and I₂. In summary, microalgae may contribute to a large variety of nutrients, yet the contents differ between kingdoms, cultivation phases and also species.

Microalgae Produce Antioxidant Molecules with Potential Preventive Effects on Mitochondrial Functions and Skeletal Muscular Oxidative Stress

In recent years, microalgae have become a source of molecules for a healthy life. Their composition of carbohydrates, peptides, lipids, vitamins and carotenoids makes them a promising new source of antioxidant molecules. Skeletal muscle is a tissue that requires constant remodeling via protein turnover, and its regular functioning consumes energy in the form of adenosine triphosphate (ATP), which is produced by mitochondria. Under conditions of traumatic exercise or muscular diseases, a high production of reactive oxygen species (ROS) at the origin of oxidative stress (OS) will lead to inflammation and muscle atrophy, with life-long consequences. In this review, we describe the potential antioxidant effects of microalgae and their biomolecules on mitochondrial functions and skeletal muscular oxidative stress during exercises or in musculoskeletal diseases, as in sarcopenia, chronic obstructive pulmonary disease (COPD) and Duchenne muscular dystrophy (DMD), through the increase in and regulation of antioxidant pathways and protein synthesis.

Bioactivity of Macronutrients from Chlorella in Physical Exercise

Chlorella is a marine microalga rich in proteins and containing all the essential amino acids. Chlorella also contains fiber and other polysaccharides, as well as polyunsaturated fatty acids such as linoleic acid and alpha-linolenic acid. The proportion of the different macronutrients in Chlorella can be modulated by altering the conditions in which it is cultured. The bioactivities of these macronutrients make Chlorella a good candidate food to include in regular diets or as the basis of dietary supplements in exercise-related nutrition both for recreational exercisers and professional athletes. This paper reviews current knowledge of the effects of the macronutrients in Chlorella on physical exercise, specifically their impact on performance and recovery. In general, consuming Chlorella improves both anaerobic and aerobic exercise performance as well as physical stamina and reduces fatigue. These effects seem to be related to the antioxidant, anti-inflammatory, and metabolic activity of all its macronutrients, while each component of Chlorella contributes its bioactivity via a specific action. Chlorella is an excellent dietary source of high-quality protein in the context of physical exercise, as dietary proteins increase satiety, activation of the anabolic mTOR (mammalian Target of Rapamycin) pathway in skeletal muscle, and the thermic effects of meals. Chlorella proteins also increase intramuscular free amino acid levels and enhance the ability of the muscles to utilize them during exercise. Fiber from Chlorella increases the diversity of the gut microbiota, which helps control body weight and maintain intestinal barrier integrity, and the production of short-chain fatty acids (SCFAs), which improve physical performance. Polyunsaturated fatty acids (PUFAs) from Chlorella contribute to endothelial protection and modulate the fluidity and rigidity of cell membranes, which may improve performance. Ultimately, in contrast to several other nutritional sources, the use of Chlorella to provide high-quality protein, dietary fiber, and bioactive fatty acids may also significantly contribute to a sustainable world through the fixation of carbon dioxide and a reduction of the amount of land used to produce animal feed.

Preparation and Characterization of Microalgae Styrene-Butadiene Composites Using Chlorella vulgaris and Arthrospira platensis Biomass

The food industry is a high consumer of polymer packing materials, sealing materials, and engineering components used in production equipment. Biobased polymer composites used in the food industry are obtained by incorporating different biogenic materials into the structure of a base polymer matrix. Renewable resources such as microalgae, bacteria, and plants may be used as biogenic materials for this purpose. Photoautotrophic microalgae are valuable microorganisms that are able to harvest sunlight energy and capture CO2 into biomass. They are characterized by their metabolic adaptability to environmental conditions, higher photosynthetic efficiency than terrestrial plants, and natural macromolecules and pigments. The flexibility of microalgae to grow in either low-nutrient or nutrient-rich environments (including wastewater) has led to the attention for their use in various biotechnological applications. Carbohydrates, proteins, and lipids are the main three classes of macromolecular compounds contained in microalgal biomass. The content in each of these components depends on their growth conditions. In general, proteins represent 40-70% of microalgae dry biomass, followed by carbohydrates (10-30%) and lipids (5-20%). A distinctive feature of microalgae cells is the presence of light-harvesting compounds such as photosynthetic pigments carotenoids, chlorophylls, and phycobilins, which are also receiving growing interest for applications in various industrial fields. The study comparatively reports on polymer composites obtained with biomass made of two species of green microalgae: Chlorella vulgaris and filamentous, gram-negative cyanobacterium Arthrospira. Experiments were conducted to reach an incorporation ratio of the biogenic material into the matrix in the 5-30% range, and the resulting materials were characterized by their mechanical and physicochemical properties.

Industry chain and challenges of microalgal food industry-a review

Currently, the whole world is facing hunger due to the increase in the global population and the rising level of food consumption. Unfortunately, the impact of environmental, climate, and political issues on agriculture has resulted in limited global food resources. Thus, it is important to develop new food sources that are environmentally friendly and not subject to climate or space limitations. Microalgae represent a potential source of nutrients and bioactive components for a wide range of high-value products. Advances in cultivation and genetic engineering techniques provide prospective approaches to widen their application for food. However, there are currently problems in the microalgae food industry in terms of assessing nutritional value, selecting processes for microalgae culture, obtaining suitable commercial strains of microalgae, etc. Additionally, the limitations of real data of market opportunities for microalgae make it difficult to assess their actual potential and to develop a better industrial chain. This review addresses the current status of the microalgae food industry, the process of commercializing microalgae food and breeding methods. Current research progress in addressing the limitations of microalgae industrialization and future prospects for developing microalgae food products are discussed.

Genomic analysis and biochemical profiling of an unaxenic strain of Synechococcus sp. isolated from the Peruvian Amazon Basin region

Cyanobacteria are diverse photosynthetic microorganisms able to produce a myriad of bioactive chemicals. To make possible the rational exploitation of these microorganisms, it is fundamental to know their metabolic capabilities and to have genomic resources. In this context, the main objective of this research was to determine the genome features and the biochemical profile of Synechococcus sp. UCP002. The cyanobacterium was isolated from the Peruvian Amazon Basin region and cultured in BG-11 medium. Growth parameters, genome features, and the biochemical profile of the cyanobacterium were determined using standardized methods. Synechococcus sp. UCP002 had a specific growth rate of 0.086 ± 0.008 μ and a doubling time of 8.08 ± 0.78 h. The complete genome of Synechococcus sp. UCP002 had a size of ∼3.53 Mb with a high coverage (∼200x), and its quality parameters were acceptable (completeness = 99.29%, complete and single-copy genes = 97.5%, and contamination = 0.35%). Additionally, the cyanobacterium had six plasmids ranging from 24 to 200 kbp. The annotated genome revealed ∼3,422 genes, ∼ 3,374 protein-coding genes (with ∼41.31% hypothetical protein-coding genes), two CRISPR Cas systems, and 61 non-coding RNAs. Both the genome and plasmids had the genes for prokaryotic defense systems. Additionally, the genome had genes coding the transcription factors of the metalloregulator ArsR/SmtB family, involved in sensing heavy metal pollution. The biochemical profile showed primary nutrients, essential amino acids, some essential fatty acids, pigments (e.g., all-trans-β-carotene, chlorophyll a, and phycocyanin), and phenolic compounds. In conclusion, Synechococcus sp. UCP002 shows biotechnological potential to produce human and animal nutrients and raw materials for biofuels and could be a new source of genes for synthetic biological applications.

Algae as Food in Europe: An Overview of Species Diversity and Their Application

Algae have been consumed for millennia in several parts of the world as food, food supplements, and additives, due to their unique organoleptic properties and nutritional and health benefits. Algae are sustainable sources of proteins, minerals, and fiber, with well-balanced essential amino acids, pigments, and fatty acids, among other relevant metabolites for human nutrition. This review covers the historical consumption of algae in Europe, developments in the current European market, challenges when introducing new species to the market, bottlenecks in production technology, consumer acceptance, and legislation. The current algae species that are consumed and commercialized in Europe were investigated, according to their status under the European Union (EU) Novel Food legislation, along with the market perspectives in terms of the current research and development initiatives, while evaluating the interest and potential in the European market. The regular consumption of more than 150 algae species was identified, of which only 20% are approved under the EU Novel Food legislation, which demonstrates that the current legislation is not broad enough and requires an urgent update. Finally, the potential of the European algae market growth was indicated by the analysis of the trends in research, technological advances, and market initiatives to promote algae commercialization and consumption.

An insight to the therapeutic potential of algae-derived sulfated polysaccharides and polyunsaturated fatty acids: Focusing on the COVID-19

Covid-19 pandemic severely affected human health worldwide. The rapidly increasing COVID-19 cases and successive mutations of the virus have made it a major challenge for scientists to find the best and efficient drug/vaccine/strategy to counteract the virus pathogenesis. As a result of research in scientific databases, regulating the immune system and its responses with nutrients and nutritional interventions is the most critical solution to prevent and combat this infection. Also, modulating other organs such as the intestine with these compounds can lead to the vaccines' effectiveness. Marine resources, mainly algae, are rich sources of nutrients and bioactive compounds with known immunomodulatory properties and the gut microbiome regulations. According to the purpose of the review, algae-derived bioactive compounds with immunomodulatory activities, sulfated polysaccharides, and polyunsaturated fatty acids have a good effect on the immune system. In addition, they have probiotic/prebiotic properties in the intestine and modulate the gut microbiomes; therefore, they can increase the effectiveness of vaccines produced. Thus, they with respectable safety, immune regulation, and modulation of microbiota have potential therapeutic against infections, especially COVID-19. They can also be employed as promising candidates for the prevention and treatment of viral infections, such as COVID-19.

Phytochemical and Potential Properties of Seaweeds and Their Recent Applications: A Review

Since ancient times, seaweeds have been employed as source of highly bioactive secondary metabolites that could act as key medicinal components. Furthermore, research into the biological activity of certain seaweed compounds has progressed significantly, with an emphasis on their composition and application for human and animal nutrition. Seaweeds have many uses: they are consumed as fodder, and have been used in medicines, cosmetics, energy, fertilizers, and industrial agar and alginate biosynthesis. The beneficial effects of seaweed are mostly due to the presence of minerals, vitamins, phenols, polysaccharides, and sterols, as well as several other bioactive compounds. These compounds seem to have antioxidant, anti-inflammatory, anti-cancer, antimicrobial, and anti-diabetic activities. Recent advances and limitations for seaweed bioactive as a nutraceutical in terms of bioavailability are explored in order to better comprehend their therapeutic development. To further understand the mechanism of action of seaweed chemicals, more research is needed as is an investigation into their potential usage in pharmaceutical companies and other applications, with the ultimate objective of developing sustainable and healthier products. The objective of this review is to collect information about the role of seaweeds on nutritional, pharmacological, industrial, and biochemical applications, as well as their impact on human health.

Antioxidant and Antimicrobial Activity of Algal and Cyanobacterial Extracts: An In Vitro Study

Algae and cyanobacteria, other than their nutritional value, possess different beneficial properties, including antioxidant and antimicrobial ones. Therefore, they can be considered functional ingredients in animal feed and natural substitutes for antibiotics. The aim of this study was to evaluate the antioxidant and antimicrobial capacity against porcine O138 E. coli of Ascophyllum nodosum, Chlorella vulgaris, Lithotamnium calcareum, Schizochytrium spp. as algal species and Arthrospira platensis as cyanobacteria. The antioxidant capacity was determined by ABTS Radical Cation Decolorization Assay testing at three different concentrations (100%; 75%; 50%). The growth inhibition effect of the extracts at concentrations of 25%, 12.5%, 6%, 3% and 1.5% against porcine O138 E. coli was genetically characterized by PCR to detect the presence of major virulence factors; this was evaluated by following the microdilution bacterial growth method. The ABTS assay disclosed that Ascophyllum nodosum was the compound with the major antioxidant properties (57.75 ± 1.44 percentage of inhibition; p < 0.0001). All the extracts tested showed growth inhibition activity at a concentration of 25%. Among all extracts, A. nodosum was the most effective, showing a significant growth inhibition of E. coli; in particular, the log10 cells/mL of E. coli used as a control resulted in a significantly higher concentration of 25% and 12.5% after 4 h (8.45 ± 0.036 and 7.22 ± 0.025 log10 cells/mL, respectively; p < 0.005). This also suggests a dose-dependent relationship between the inhibitory activity and the concentration. Also, a synergistic effect was observed on antioxidant activity for the combination of Ascophyllum nodosum and Lithotamnium calcareum (p < 0.0001). Moreover, to determine if this combination could affect the viability of the IPEC-J2 cells under the normal or stress condition, the viability and membrane integrity were tested, disclosing that the combination mitigated the oxidative stress experimentally induced by increasing the cell viability. In conclusion, the results obtained highlight that the bioactive compounds of algal species are able to exert antioxidant capacity and modulate O138 E. coli growth. Also, the combination of Ascophyllum nodosum and Lithotamnium calcareum species can enhance their bioactivity, making them a promising functional feed additive and a suitable alternative to antibiotics.

Biofixation of Air Emissions and Biomass Valorization-Evaluation of Microalgal Biotechnology

This research appraised the simultaneous biofixation, that is not quite common in scientific literature, of carbon dioxide (CO₂) and nitric oxides (NO_x) by microalgae species Chlorella vulgaris, Haematococcus pluvialis, and Scenedesmus subspicatus. The experimental design was established by five treatments with gas concentrations between control-0.04% of CO₂, 5 to 15% of CO₂, and 30 to 100 ppm of NOx. Parameters such as pH, growth, productivity, lipids, protein, carbon/ nitrogen ratio, and astaxanthin were evaluated. For all species, the maximal growth and productivity were achieved with 5% of CO₂ and 30 ppm of NO_x. Regarding protein content, for all the three species, better results were obtained at higher concentrations of CO₂ and NOx. These results prove the microalgae capacity for CO₂ and NO_x biofixation and reuse of biomass as a source of high value-added products, such as lipids, proteins, and astaxanthin. These findings support the indication of these species for flue gas treatment process and use in biorefineries systems.

Influence of Carbon Sources on Biomass and Biomolecule Accumulation in Picochlorum sp. Cultured under the Mixotrophic Condition

The major downfalls of the microalgal biorefinery are low volume of high value product accumulation, low biomass productivity and high cultivation costs. Here, we aimed to improve the biomass productivity of the industrially relevant Picochlorum sp. BDUG 100241 strain. The growth of Picochlorum sp. BDUG 100241 was investigated under different cultivations conditions, including photoautotrophic (with light), mixotrophic (1% glucose, with light) and heterotrophic (1% glucose, without light). Among them, Picochlorum sp. BDUG100241 showed the highest growth in the mixotrophic condition. Under different (1%) carbon sources’ supplementation, including glucose, sodium acetate, glycerol, citric acid and methanol, Picochlorum sp. BDUG100241 growth was tested. Among them, sodium acetate was found to be most suitable carbon source for Picochlorum sp. BDUG 100241 growth, biomass (1.67 ± 0.18 g/L) and biomolecule productivity. From the different concentrations of sodium acetate (0, 2.5, 5.0, 7.5 and 10 g/L) tested, the maximum biomass production of 2.40 ± 0.20 g/L with the biomass productivity of 95 ± 5.00 mg/L/d was measured from 7.5 g/L in sodium acetate. The highest total lipid (53.50 ± 1.70%) and total carotenoids (0.75 ± 0.01 µg/mL) contents were observed at the concentration of 7.5 g/L and 5.0 g/L of sodium acetate as a carbon source, respectively. In conclusion, the mixotrophic growth condition containing 7.5 g/L of sodium acetate showed the maximum biomass yield and biomolecule accumulation compared to other organic carbon sources.

Coelastrella terrestris for Adonixanthin Production: Physiological Characterization and Evaluation of Secondary Carotenoid Productivity

A novel strain of Coelastrella terrestris (Chlorophyta) was collected from red mucilage in a glacier foreland in Iceland. Its morphology showed characteristic single, ellipsoidal cells with apical wart-like wall thickenings. Physiological characterization revealed the presence of the rare keto-carotenoid adonixanthin, as well as high levels of unsaturated fatty acids of up to 85%. Initial screening experiments with different carbon sources for accelerated mixotrophic biomass growth were done. Consequently, a scale up to 1.25 L stirred photobioreactor cultivations yielded a maximum of 1.96 mg·L⁻¹ adonixanthin in free and esterified forms. It could be shown that supplementing acetate to the medium increased the volumetric productivity after entering the nitrogen limitation phase compared to autotrophic control cultures. This study describes a promising way of biotechnological adonixanthin production using Coelastrella terrestris.

Biodegradable Solvents: A Promising Tool to Recover Proteins from Microalgae

The world will face a significant protein demand in the next few decades, and due to the environmental concerns linked to animal protein, new sustainable protein sources must be found. In this regard, microalgae stand as an outstanding high-quality protein source. However, different steps are needed to separate the proteins from the microalgae biomass and other biocompounds. The protein recovery from the disrupted biomass is usually the bottleneck of the process, and it typically employs organic solvents or harsh conditions, which are both detrimental to protein stability and planet health. Different techniques and methods are applied for protein recovery from various matrices, such as precipitation, filtration, chromatography, electrophoresis, and solvent extraction. Those methods will be reviewed in this work, discussing their advantages, drawbacks, and applicability to the microalgae biorefinery process. Special attention will be paid to solvent extraction performed with ionic liquids (ILs) and deep eutectic solvents (DESs), which stand as promising solvents to perform efficient protein separations with reduced environmental costs compared to classical alternatives. Finally, several solvent recovery options will be analyzed to reuse the solvent employed and isolate the proteins from the solvent phase.

Evaluation of Nutraceutical Properties of Eleven Microalgal Strains Isolated from Different Freshwater Aquatic Environments: Perspectives for Their Application as Nutraceuticals

The increasing global population and the simultaneous growing attention to natural, sustainable, and healthier products are driving the food industry towards research on alternative food sources. In this scenario, microalgae are gaining worldwide attention as "functional feedstocks" for foods, feeds, supplements, and nutraceutical formulations, being a source of high-value metabolites including polyphenols and other antioxidant compounds. In this work, eleven microalgal strains from freshwater environments were evaluated for their nutraceutical properties, focusing on photosynthetic pigments, total polyphenols, and flavonoid content, as well as in vitro antioxidant activities. Data helped to select those strains showing the most promising features for simultaneous massive growth and bioactive compound production. Results highlighted that the microalgae have variable values for both biochemical parameters and antioxidant activities, mainly depending on the solvents and applied treatment rather than on the isolation sources or the phylogenetic attribution. According to our results, the putative best candidates for massive cultivation under laboratory conditions for the simultaneous extraction of different molecules with nutraceutical potential are strains F1 (Scenedesmaceae), F3 (Chlamydomonas debariana), R1 (Chlorella sorokiniana), and C2 (Chlorella-like).

Biotechnological Enhancement of Probiotics through Co-Cultivation with Algae: Future or a Trend?

The diversity of algal species is a rich source of many different bioactive metabolites. The compounds extracted from algal biomass have various beneficial effects on health. Recently, co-culture systems between microalgae and bacteria have emerged as an interesting solution that can reduce the high contamination risk associated with axenic cultures and, consequently, increase biomass yield and synthesis of active compounds. Probiotic microorganisms also have numerous positive effects on various aspects of health and represent potent co-culture partners. Most studies consider algae as prebiotics that serve as enhancers of probiotics performance. However, the extreme diversity of algal organisms and their ability to produce a plethora of metabolites are leading to new experimental designs in which these organisms are cultivated together to derive maximum benefit from their synergistic interactions. The future success of these studies depends on the precise experimental design of these complex systems. In the last decade, the development of high-throughput approaches has enabled a deeper understanding of global changes in response to interspecies interactions. Several studies have shown that the addition of algae, along with probiotics, can influence the microbiota, and improve gut health and overall yield in fish, shrimp, and mussels aquaculture. In the future, such findings can be further explored and implemented for use as dietary supplements for humans.

Wastewater-based microalgal biorefineries for the production of astaxanthin and co-products: Current status, challenges and future perspectives

The freshwater microalgae Haematococcus pluvialis and Chlorella zofingiensis are attractive biorefinery feedstocks in view of their ability to simultaneously synthesize astaxanthin and other valuable metabolites. Nonetheless, there are concerns regarding the sustainability of such biorefineries due to the high freshwater footprint of microalgae cultivation. The integration of wastewater as an alternative growth media is a promising approach to reduce freshwater demand. Wastewater-based cultivation enables the recovery of essential nutrients required for microalgae growth and consequently results in phycoremediation of wastewater, thus promoting the concept of a circular economy and further enhancing the sustainability of the process. In this review, recent developments in wastewater-integrated cultivation of H. pluvialis and C. zofingiensis for astaxanthin production are discussed. Furthermore, prospective strategies for overcoming the inherent challenges of wastewater-based cultivation are reviewed. Moreover, the biorefinery potential of wastewater-grown H. pluvialis and C. zofingiensis is delineated and future perspectives of wastewater-based biorefineries are outlined.

Immune Status and Hepatic Antioxidant Capacity of Gilthead Seabream Sparus aurata Juveniles Fed Yeast and Microalga Derived β-glucans

This work aimed to evaluate the effects of dietary supplementation with β-glucans extracted from yeast (Saccharomyces cerevisiae) and microalga (Phaeodactylum tricornutum) on gene expression, oxidative stress biomarkers and plasma immune parameters in gilthead seabream (Sparus aurata) juveniles. A practical commercial diet was used as the control (CTRL), and three others based on CTRL were further supplemented with different β-glucan extracts. One was derived from S. cerevisiae (diet MG) and two different extracts of 21% and 37% P. tricornutum-derived β-glucans (defined as Phaeo21 and Phaeo37), to give a final 0.06% β-glucan dietary concentration. Quadruplicate groups of 95 gilthead seabream (initial body weight: 4.1 ± 0.1 g) were fed to satiation three times a day for 8 weeks in a pulse-feeding regimen, with experimental diets intercalated with the CTRL dietary treatment every 2 weeks. After 8 weeks of feeding, all groups showed equal growth performance and no changes were found in plasma innate immune status. Nonetheless, fish groups fed β-glucans supplemented diets showed an improved anti-oxidant status compared to those fed CTRL at both sampling points (i.e., 2 and 8 weeks). The intestinal gene expression analysis highlighted the immunomodulatory role of Phaeo37 diet after 8 weeks, inducing an immune tolerance effect in gilthead seabream intestine, and a general down-regulation of immune-related gene expression. In conclusion, the results suggest that the dietary pulse administration of a P. tricornutum 37% enriched-β-glucans extract might be used as a counter-measure in a context of gut inflammation, due to its immune-tolerant and anti-oxidative effects.

Concurrent enhancement of CO2 fixation and productivities of omega-3 fatty acids and astaxanthin in Haematococcus pluvialis culture via calcium-mediated homeoviscous adaptation and biomineralization

Haematococcus pluvialis has attracted interest as a bio-platform for producing omega-3 fatty acids (ω-3 FA) and astaxanthin that have a great potential as anti-inflammatory drugs. This study aimed to concurrently enhance the CO₂ fixation and the productivities of ω-3 FA and astaxanthin, which have been difficult to achieve because of the dissimilar culture methods for each goal, via calcium-mediated homeoviscous adaptation and biomineralization. As a result of 3 mM of Ca²⁺ addition, ω-3 FA content was improved by 31% due to Ca²⁺-induced homeoviscous adaptation. Biomineralization was promoted by the extracellular carbonic anhydrase, which resulted in 46.3% improvement in CO₂ fixation. CaCO₃ from the biomineralization was beneficially re-used in the H. pluvialis culture and triggered 178- and 522-fold increased biomass productivity and astaxanthin content, respectively, thanks to its anisotropic nature. The Ca²⁺-based productivity enhancement strategy was applied to large-scale culture which resulted improvement in overall bioprocess performance.

Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

Third-generation biofuels that are derived from microalgal biomass have gained momentum as a way forward in the sustainable production of biodiesel. Such efforts are propelled by the intention to reduce our dependence on fossil fuels as the primary source of energy. Accordingly, growing microalgal biomass in the form of suspended cultivation has been a conventional technique for the past few decades. To overcome the inevitable harvesting shortcomings arising from the excessive energy and time needed to separate the planktonic microalgal cells from water medium, researchers have started to explore attached microalgal cultivation systems. This cultivation mode permits the ease of harvesting mature microalgal biomass, circumventing the need to employ complex harvesting techniques to single out the cells, and is economically attractive. However, the main bottleneck associated with attached microalgal growth is low biomass production due to the difficulties the microalgal cells have in forming attachment and populating thereafter. In this regard, the current review encompasses the novel techniques adopted to promote attached microalgal growth. The physicochemical effects such as the pH of the culture medium, hydrophobicity, as well as the substratum surface properties and abiotic factors that can determine the fate of exponential growth of attached microalgal cells, are critically reviewed. This review aims to unveil the benefits of an attached microalgal cultivation system as a promising harvesting technique to produce sustainable biodiesel for lasting applications.

Multi-product biorefinery from Arthrospira platensis biomass as feedstock for bioethanol and lactic acid production

With the aim to reach the maximum recovery of bulk and specialty bioproducts while minimizing waste generation, a multi-product biorefinery for ethanol and lactic acid production from the biomass of cyanobacterium Arthrospira platensis was investigated. Therefore, the residual biomass resulting from different pretreatments consisting of supercritical fluid extraction (SF) and microwave assisted extraction with non-polar (MN) and polar solvents (MP), previously applied on A. platensis to extract bioactive metabolites, was further valorized. In particular, it was used as a substrate for fermentation with Saccharomyces cerevisiae LPB-287 and Lactobacillus acidophilus ATCC 43121 to produce bioethanol (BE) and lactic acid (LA), respectively. The maximum concentrations achieved were 3.02 ± 0.07 g/L of BE by the MN process at 120 rpm 30 °C, and 9.67 ± 0.05 g/L of LA by the SF process at 120 rpm 37 °C. An economic analysis of BE and LA production was carried out to elucidate the impact of fermentation scale, fermenter costs, production titer, fermentation time and cyanobacterial biomass production cost. The results indicated that the critical variables are fermenter scale, equipment cost, and product titer; time process was analyzed but was not critical. As scale increased, costs tended to stabilize, but also more product was generated, which causes production costs per unit of product to sharply decrease. The median value of production cost was US$ 1.27 and US$ 0.39, for BE and LA, respectively, supporting the concept of cyanobacterium biomass being used for fermentation and subsequent extraction to obtain ethanol and lactic acid as end products from A. platensis.

Exopolysaccharides from microalgae: production, characterization, optimization and techno-economic assessment

Microalgae cultivation for exopolysaccharide production has getting more attention as a result of their high hydrocarbon biosynthesis skill. The aim of this study is to examine the exopolysaccharide production potential of different species of microalgae. In this context, exopolysaccharides were produced from Chlorella minutissima, Chlorella sorokiniana and Botryococcus braunii microalgae and the effects of carbon and nitrogen content in the growth medium and illumination time on exopolysaccharide production were analyzed statistically using Box-Behnken experimental design. In addition, techno-economic assessment of exopolysaccharide production were also performed by using the most productive microalgae and optimum conditions determined in this study. As a result of the experiments, it was seen that C. minutissima, C. sorokiniana and B. braunii produced 0.245 ± 0.0025 g/L, 0.163 ± 0.0016 g/L and 0.117 ± 0.0007 g/L exopolysaccharide, respectively. Statistically, it was observed that there was an inverse relationship between the exopolysaccharide production and investigated parameters such as illumination period and carbon and nitrogen amounts of culture mediums. The techno-economic assessment comprising microalgal exopolysaccharide (EPS) bioprocess was carried out, and it showed that the system can be considered economically viable, yet can be improved with biorefinery approach.

Preparation of the Enzymatic Hydrolysates from Chlorella vulgaris Protein and Assessment of Their Antioxidant Potential Using Caenorhabditis elegans

This study aimed to assess the antioxidant potential of Chlorella vulgaris protein-derived enzymatic hydrolysate using Caenorhabditis elegans. Protein extraction was performed using an alkali solution after complete C. vulgaris swelling and hydrolysis using four commercial proteases (alcalase, neutrase, protamex, and flavourzyme). The results showed that the flavourzyme hydrolysates exhibited the strongest antioxidant activity both in vitro and in vivo. Under the optimum conditions of the enzymatic hydrolysis, the half-maximal effective concentration of the hydrolysates for superoxide and hydroxyl radicals was 0.323 mg/mL and 0.139 mg/mL, respectively. The hydrolysates could significantly extend the lifespan, improve the resistance to methyl viologen-induced oxidative stress, reduce the levels of reactive oxygen species, and enhance the activity of catalase and superoxide dismutase in C. elegans.

Appetite Regulation, Growth Performances and Fish Quality Are Modulated by Alternative Dietary Protein Ingredients in Gilthead Sea Bream (Sparus aurata) Culture

Simple Summary

In a world dramatically harassed by climate changes and overexploitation of resources, the aquaculture expansion poses several challenges. Among the others, aquafeed formulations need to be rethought in a circular economy vision, avoiding food-feed competition, and possibly valorizing one or more ingredients for their functionality. In this context, the present trial showed that Hermetia illucens prepupae, poultry-by products, and red swamp crayfish meals can effectively replace a substantial proportion of vegetable proteins in the diet for gilthead seabream (Sparus aurata) without impairing fish growth and fillet quality. On the contrary, a blend of Tisochrysis lutea and Tetraselmis suecica negatively impacted fish growth and further studies are thus necessary to better valorize their natural content in pigments in fish farming.

Abstract

By answering the need for increasing sustainability in aquaculture, the present study aimed to compare growth, gene expression involved in appetite regulation, physical characteristics, and chemical composition of Sparus aurata fed alternative protein sources. Fish were fed ten iso-proteic, iso-lipidic, and isoenergetic diets: a vegetable-based (CV) and a marine ingredient-rich (CF) diet were set as control diets. The others were prepared by replacing graded levels (10, 20 or 40%) of the vegetable proteins in the CV with proteins from a commercial defatted Hermetia illucens pupae meal (H), poultry by-product meal (PBM) singly (H10, H20, H40, P20, P40) or in combination (H10P30), red swamp crayfish meal (RC10) and from a blend (2:1, w:w) of Tisochrysis lutea and Tetraselmis suecica (MA10) dried biomasses. The increase in ghre gene expression observed in MA10 fed fish matched with increased feed intake and increased feed conversion ratio. Besides, the MA10 diet conferred a lighter aspect to the fish skin (p < 0.05) than the others. Overall, no detrimental effects of H, PBM, and RC meal included in the diets were observed, and fish fatty acid profile resulted as comparable among these groups and CV, thus demonstrating the possibility to introduce H, PBM, and RC in partial replacement of vegetable proteins in the diet for Sparus aurata.

Lipids from Microalgae for Cosmetic Applications

In recent years, there has been considerable interest in using microalgal lipids in the food, chemical, pharmaceutical, and cosmetic industries. Several microalgal species can accumulate appreciable lipid quantities and therefore are characterized as oleaginous. In cosmetic formulations, lipids and their derivatives are one of the main ingredients. Different lipid classes are great moisturizing, emollient, and softening agents, work as surfactants and emulsifiers, give consistence to products, are color and fragrance carriers, act as preservatives to maintain products integrity, and can be part of the molecules delivery system. In the past, chemicals have been widely used but today’s market and customers’ demands are oriented towards natural products. Microalgae are an extraordinary source of lipids and other many bioactive molecules. Scientists’ attention to microalgae cultivation for their industrial application is increasing. For the high costs associated, commercialization of microalgae and their products is still not very widespread. The possibility to use biomass for various industrial purposes could make microalgae more economically competitive.

Variability in Macro- and Micronutrients of 15 Commercially Available Microalgae Powders

The nutrient composition of 15 commercially available microalgae powders of Arthrospira platensis, Chlorella pyrenoidosa and vulgaris, Dunaliella salina, Haematococcus pluvialis, Tetraselmis chuii, and Aphanizomenon flos-aquae was analyzed. The Dunaliella salina powders were characterized by a high content of carbohydrates, saturated fatty acids (SFAs), omega-6-polyunsaturated fatty acids (n6-PUFAs), heavy metals, and α-tocopherol, whereas the protein amounts, essential amino acids (EAAs), omega-3-PUFAs (n3-PUFAs), vitamins, and minerals were low. In the powder of Haematococcus pluvialis, ten times higher amounts of carotenoids compared to all other analyzed powders were determined, yet it was low in vitamins D and E, protein, and EAAs, and the n6/n3-PUFAs ratio was comparably high. Vitamin B₁₂, quantified as cobalamin, was below 0.02 mg/100 g dry weight (d.w.) in all studied powders. Based on our analysis, microalgae such as Aphanizomenon and Chlorella may contribute to an adequate intake of critical nutrients such as protein with a high content of EAAs, dietary fibers, n3-PUFAs, Ca, Fe, Mg, and Zn, as well as vitamin D and E. Yet, the nutritional value of Aphanizomenon flos-aquae was slightly decreased by high contents of SFAs. The present data show that microalgae are rich in valuable nutrients, but the macro- and micronutrient profiles differ strongly between and within species.

Microbial Resources, Fermentation and Reduction of Negative Externalities in Food Systems: Patterns toward Sustainability and Resilience

One of the main targets of sustainable development is the reduction of environmental, social, and economic negative externalities associated with the production of foods and beverages. Those externalities occur at different stages of food chains, from the farm to the fork, with deleterious impacts to different extents. Increasing evidence testifies to the potential of microbial-based solutions and fermentative processes as mitigating strategies to reduce negative externalities in food systems. In several cases, innovative solutions might find in situ applications from the farm to the fork, including advances in food matrices by means of tailored fermentative processes. This viewpoint recalls the attention on microbial biotechnologies as a field of bioeconomy and of ‘green’ innovations to improve sustainability and resilience of agri-food systems alleviating environmental, economic, and social undesired externalities. We argue that food scientists could systematically consider the potential of microbes as ‘mitigating agents’ in all research and development activities dealing with fermentation and microbial-based biotechnologies in the agri-food sector. This aims to conciliate process and product innovations with a development respectful of future generations’ needs and with the aptitude of the systems to overcome global challenges.

Performance of Single and Two-Stage Cross-Flow Ultrafiltration Membrane in Fractionation of Peptide from Microalgae Protein Hydrolysate (Nannochloropsis gaditana)

Cross-flow ultrafiltration (UF) membrane with two different configurations; single (10 kDa and 5 kDa) and two-stage (10/5 kDa) in fractionating microalgae protein hydrolysate (MPH) were studied to obtain a low molecular weight of peptide. The effect of flow rate, trans-membrane pressure (TMP), and pH in fractionating MPH were evaluated based on permeate flux and peptide transmission. The results showed that, for single UF membrane, optimum operating parameters were at a flow rate of 23 mL/min, TMP of 1.5 bar, and pH of 9, with permeate flux of 43.65 L/m2 h (10 kDa) and 55.42 L/m2 h (5 kDa) and peptide transmission of 58.20% (10 kDa) and 67.34% (5 kDa). Meanwhile, for two-stage (10/5 kDa) UF membrane, the best parameters were observed at a flow rate of 23 mL/min, TMP of 1.5 bar, and pH of 2, with permeate flux of 69.85 L/m2 h and peptide transmission of 79.13%. Fractionation of MPH with two-stage UF membrane was observed to be better at producing a low molecular weight of peptide compared to single UF membrane. In conclusion, it was possible to produce permeate flux with a high amount of low molecular weight of peptide by controlling the operating parameters with the suitable configuration membrane.

Illumination Policies for Stichococcus sp. Cultures in an Optimally Operating Lab-Scale PBR toward the Directed Photosynthetic Production of Desired Products

The light spectrum effect on the cultivation efficiency of the microalgae strain Stichococcus sp. is explored, as a means of potentially intensifying the biomass productivity and regulating the cellular composition. Stichococcus sp. batch culture experiments, within a 3 L bench-top photobioreactor (PBR), are designed and implemented under different light spectrum profiles (i.e., cool white light (WL), cool white combined with red light (WRL), and cool white combined with blue light, (WBL)). The obtained results indicate that the studied strain is capable of adapting its metabolite profile to the light field to which it is exposed. The highest biomass concentration (3.5 g/L), combined with intense carbohydrate accumulation activity, resulting in a respective final concentration of 1.15 g/L was achieved within 17 days using exclusively cool white light of increasing intensity. The addition of blue light emitting diodes (LED) light, combined with appropriately selected culture conditions, contributed significantly to the massive synthesis and accumulation of lipids, resulting in a concentration of 1.43 g/L and a respective content of 46.13% w/w, with a distinct impact on biomass, carbohydrates and proteins productivity. Finally, a beneficial contribution of red LED light to the protein synthesis is recognized and this can be conditionally amplified provided nitrogen sufficiency in the culture medium.

Tetraedron minimum, First Reported Member of Hydrodictyaceae to Accumulate Secondary Carotenoids

We isolated a novel strain of the microalga Tetraedron minimum in Iceland from a terrestrial habitat. During long-term cultivation, a dish culture turned orange, indicating the presence of secondary pigments. Thus, we characterized T. minimum for growth and possible carotenoid production in different inorganic media. In a lab-scale photobioreactor, we confirmed that nitrogen starvation in combination with salt stress triggered a secondary carotenoid accumulation. The development of the pigment composition and the antioxidant capacity of the extracts was analyzed throughout the cultivations. The final secondary carotenoid composition was, on average, 61.1% astaxanthin and 38.9% adonixanthin. Moreover, the cells accumulated approx. 83.1% unsaturated fatty acids. This work presents the first report of the formation of secondary carotenoids within the family Hydrodictyaceae (Sphaeropleales, Chlorophyta).

Evaluation of Microalgae as Immunostimulants and Recombinant Vaccines for Diseases Prevention and Control in Aquaculture

Microalgae are often used as nutritional supplements for aquatic animals and are widely used in the aquaculture industry, providing direct or indirect nutrients for many aquatic animals. Microalgae are abundant in nature, of high nutritional value, and some of them are non-toxic and rich in antioxidants so that they can be explored as a medicinal carrier for human or animals. Natural wild-type microalgae can be adopted as an immunostimulant to enhance non-specific immune response and improve growth performance, among which Haematococcus pluvialis, Arthrospira (Spirulina) platensis, and Chlorella spp. are commonly used. At present, there have been some successful cases of using microalgae to develop oral vaccines in the aquaculture industry. Researchers usually develop recombinant vaccines based on Chlamydomonas reinhardtii, Dunaliella salina, and cyanobacteria. Among them, in the genetic modification of eukaryotic microalgae, many examples are expressing antigen genes in chloroplasts. They are all used for the prevention and control of single infectious diseases and most of them are resistant to shrimp virus infection. However, there is still no effective strategy targeting polymicrobial infections and few commercial vaccines are available. Although several species of microalgae are widely developed in the aquaculture industry, many of them have not yet established an effective and mature genetic manipulation system. This article systematically analyzes and discusses the above problems to provide ideas for the future development of highly effective microalgae recombinant oral vaccines.

Biochemical and Nutritional Evaluation of Chlorella and Auxenochlorella Biomasses Relevant for Food Application

Microalgae are a source of potentially healthy and sustainable nutrients. However, the bioaccessibility of these nutrients remains uncertain. In this study, we analyzed the biomass composition of five commercial Chlorella and Auxenochlorella strains, and Chlorella vulgaris heterotrophically cultivated in our laboratory. Protein accounted for 65 ± 3% (w w^-1) dry matter (DM) in all biomasses, except for the lab-grown C. vulgaris that contained 20% (w w^-1) DM protein. The fatty acids content was comparable and ranged between 7 and 10% (w w^-1) DM. Most of the biomasses had a ω6-polyunsaturated fatty acids (PUFAs)/ω3-PUFAs ratio <4, as recommended by nutritional experts. A recently published harmonized protocol for in vitro digestion was used to evaluate fatty acids and protein bioaccessibilities. Protein bioaccessibility ranged between 60 and 74% for commercial Chlorella and Auxenochlorella biomasses and was 43% for the lab-grown C. vulgaris. Fatty acids bioaccessibility was <7% in commercial biomasses and 19% in the lab-grown C. vulgaris. Taken together, the results show that microalgae are promising sources of bioaccessible protein. The limited fatty acids bioaccessibility indicates the need for alternative upstream and downstream production strategies.

Astaxanthin and other Nutrients from Haematococcus pluvialis-Multifunctional Applications

Bioactive compounds of natural origin are gaining increasing popularity. High biological activity and bioavailability, beneficial effects on health and safety of use are some of their most desirable features. Low production and processing costs render them even more attractive. Microorganisms have been used in the food, medicinal, cosmetic and energy industries for years. Among them, microalgae have proved to be an invaluable source of beneficial compounds. Haematococcus pluvialis is known as the richest source of natural carotenoid called astaxanthin. In this paper, we focus on the cultivation methods of this green microalga, its chemical composition, extraction of astaxanthin and analysis of its antioxidant, anti-inflammatory, anti-diabetic and anticancer activities. H. pluvialis, as well as astaxanthin can be used not only for the treatment of human and animal diseases, but also as a valuable component of diet and feed.